Affiliations: Departamento de Tecnologia Farmacêutica, Faculdade
de Farmácia da Universidade do Porto, Porto, Portugal | REQUIMTE, Serviço de Farmacognosia, Faculdade de
Farmácia da Universidade do Porto, Porto, Portugal | Departamento de Dermatologia e Venereologia, Hospital
de São Marcos, Braga, Portugal
Note: [] Address for correspondence: Maria Fernanda Bahia, Department of
Pharmaceutical Technology, Faculdade de Farmácia, Universidade do Porto,
Rua Aníbal Cunha, 164, 4099-030 Porto, Portugal. Tel.: +351222078912; Fax:
+351222003977; E-mail: fgbahia@ff.up.pt
Abstract: The topical application of antioxidants may be beneficial for the
protection of the skin against UV damage. An extract of Quercus robur
leaves was prepared and evaluated considering its putative application as
topical antioxidant. The solvent and extractive method selection was monitored
by 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging activity and
polyphenols extraction (measured by the Folin Ciocalteu assay). Iron chelating
activity and the phenolic composition (HPLC/DAD) were assessed on the extract
obtained under optimized conditions. Skin irritation potential was investigated
by performing an in vivo patch test in 19 volunteers. The extraction
solvent which resulted in the highest activity was ethanol:water (4:6) and thus
it was selected for further preparation of this extract. The
IC_{50s} for the iron chelation and DPPH scavenging assays
were 153.8 ± 26.3 μg.mL^{-1} and 7.53 ± 0.71
μg.mL^{-1} (mean
± SD), respectively. The total phenolic content was found
to be 346.3 ± 6.7 mg gallic acid equivalents (GAE)/g
extract (mean ± SD). Three phenolic compounds were
identified in the extract namely: ellagic acid, rutin and hyperoside. The major
identified component was ellagic acid. The patch test carried out showed that
the extract can be regarded as safe for topical application.
Keywords: Quercus robur, in vivo skin irritation, antioxidant, photoaging, polyphenols, iron chelators
Journal: BioFactors, vol. 33, no. 4, pp. 267-279, 2008
